[libvirt] [PATCH v2]LXC: Helper function for checking ownership of dir when userns enabled
From: Chen Hanxiao <chenhanxiao@cn.fujitsu.com> If we enable userns, the ownership of dir we provided for containers should match the uid/gid in idmap. Currently, the debug log is very implicit or misleading sometimes. This patch will help clarify this for us when using debug log or virsh. v2: syntax-check clean Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com> --- src/lxc/lxc_container.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 46 insertions(+), 0 deletions(-) diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c index b910b10..2ccdc61 100644 --- a/src/lxc/lxc_container.c +++ b/src/lxc/lxc_container.c @@ -1815,6 +1815,49 @@ lxcNeedNetworkNamespace(virDomainDefPtr def) return false; } +/* + * Helper function for helping check + * whether we have enough privilege + * to operate the source dir when userns enabled + * @vmDef: pointer to vm definition structure + * Returns 0 on success or -1 in case of error + */ +static int +lxcContainerUsernsSrcOwnershipCheck(virDomainDefPtr vmDef) +{ + struct stat buf; + size_t i; + uid_t uid; + gid_t gid; + + VIR_DEBUG("vmDef->nfss %d", (int)vmDef->nfss); + for (i = 0; i < vmDef->nfss; i++) { + VIR_DEBUG("dst is %s, src is %s", + vmDef->fss[i]->dst, + vmDef->fss[i]->src); + + uid = vmDef->idmap.uidmap[0].target; + gid = vmDef->idmap.gidmap[0].target; + + if (lstat(vmDef->fss[i]->src, &buf) < 0) { + virReportSystemError(errno, _("Cannot access '%s'"), + vmDef->fss[i]->src); + return -1; + } else if (uid != buf.st_uid || gid != buf.st_gid) { + VIR_DEBUG("In userns uid is %d, gid is %d\n", + uid, gid); + errno = EINVAL; + + virReportSystemError(errno, + _("[userns] Src dir '%s' does not belong to uid/gid: %d/%d"), + vmDef->fss[i]->src, uid, gid); + return -1; + } + } + + return 0; +} + /** * lxcContainerStart: * @def: pointer to virtual machine structure @@ -1866,6 +1909,9 @@ int lxcContainerStart(virDomainDefPtr def, if (userns_supported()) { VIR_DEBUG("Enable user namespace"); cflags |= CLONE_NEWUSER; + if (lxcContainerUsernsSrcOwnershipCheck(def) < 0) { + return -1; + } } else { virReportSystemError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("Kernel doesn't support user namespace")); -- 1.7.1
On Fri, Aug 09, 2013 at 04:05:58PM +0800, Chen Hanxiao wrote:
From: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
If we enable userns, the ownership of dir we provided for containers should match the uid/gid in idmap. Currently, the debug log is very implicit or misleading sometimes. This patch will help clarify this for us when using debug log or virsh.
I do recall hitting some permission issue once, but can't remember just what it was. Can you describe exactly how to reproduce the problem ?
Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com> --- src/lxc/lxc_container.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 46 insertions(+), 0 deletions(-)
diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c index b910b10..2ccdc61 100644 --- a/src/lxc/lxc_container.c +++ b/src/lxc/lxc_container.c @@ -1815,6 +1815,49 @@ lxcNeedNetworkNamespace(virDomainDefPtr def) return false; }
+/* + * Helper function for helping check + * whether we have enough privilege + * to operate the source dir when userns enabled + * @vmDef: pointer to vm definition structure + * Returns 0 on success or -1 in case of error + */ +static int +lxcContainerUsernsSrcOwnershipCheck(virDomainDefPtr vmDef) +{ + struct stat buf; + size_t i; + uid_t uid; + gid_t gid; + + VIR_DEBUG("vmDef->nfss %d", (int)vmDef->nfss); + for (i = 0; i < vmDef->nfss; i++) { + VIR_DEBUG("dst is %s, src is %s", + vmDef->fss[i]->dst, + vmDef->fss[i]->src); + + uid = vmDef->idmap.uidmap[0].target; + gid = vmDef->idmap.gidmap[0].target; + + if (lstat(vmDef->fss[i]->src, &buf) < 0) { + virReportSystemError(errno, _("Cannot access '%s'"), + vmDef->fss[i]->src); + return -1; + } else if (uid != buf.st_uid || gid != buf.st_gid) { + VIR_DEBUG("In userns uid is %d, gid is %d\n", + uid, gid); + errno = EINVAL; + + virReportSystemError(errno, + _("[userns] Src dir '%s' does not belong to uid/gid: %d/%d"), + vmDef->fss[i]->src, uid, gid); + return -1; + } + } + + return 0; +} + /** * lxcContainerStart: * @def: pointer to virtual machine structure @@ -1866,6 +1909,9 @@ int lxcContainerStart(virDomainDefPtr def, if (userns_supported()) { VIR_DEBUG("Enable user namespace"); cflags |= CLONE_NEWUSER; + if (lxcContainerUsernsSrcOwnershipCheck(def) < 0) { + return -1; + } } else { virReportSystemError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("Kernel doesn't support user namespace"));
Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
-----Original Message----- From: Daniel P. Berrange [mailto:berrange@redhat.com] Sent: Saturday, August 10, 2013 12:54 AM To: Chen Hanxiao Cc: libvir-list@redhat.com Subject: Re: [libvirt] [PATCH v2]LXC: Helper function for checking ownership of dir when userns enabled
On Fri, Aug 09, 2013 at 04:05:58PM +0800, Chen Hanxiao wrote:
From: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
If we enable userns, the ownership of dir we provided for containers should match the uid/gid in idmap. Currently, the debug log is very implicit or misleading sometimes. This patch will help clarify this for us when using debug log or virsh.
I do recall hitting some permission issue once, but can't remember just what it was. Can you describe exactly how to reproduce the problem ?
1) Enable user namespace in kernel 2) Add idmap for container 3) Don't change the ownership of devices/ filesystem/ source dir ( leave them to 'root' for instance) 4) Start the container Usually I got an input/output error by virsh, which is not a good hint.
Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com> --- src/lxc/lxc_container.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 46 insertions(+), 0 deletions(-)
diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c index b910b10..2ccdc61 100644 --- a/src/lxc/lxc_container.c +++ b/src/lxc/lxc_container.c @@ -1815,6 +1815,49 @@ lxcNeedNetworkNamespace(virDomainDefPtr def) return false; }
+/* + * Helper function for helping check + * whether we have enough privilege + * to operate the source dir when userns enabled + * @vmDef: pointer to vm definition structure + * Returns 0 on success or -1 in case of error + */ +static int +lxcContainerUsernsSrcOwnershipCheck(virDomainDefPtr vmDef) +{ + struct stat buf; + size_t i; + uid_t uid; + gid_t gid; + + VIR_DEBUG("vmDef->nfss %d", (int)vmDef->nfss); + for (i = 0; i < vmDef->nfss; i++) { + VIR_DEBUG("dst is %s, src is %s", + vmDef->fss[i]->dst, + vmDef->fss[i]->src); + + uid = vmDef->idmap.uidmap[0].target; + gid = vmDef->idmap.gidmap[0].target; + + if (lstat(vmDef->fss[i]->src, &buf) < 0) { + virReportSystemError(errno, _("Cannot access '%s'"), + vmDef->fss[i]->src); + return -1; + } else if (uid != buf.st_uid || gid != buf.st_gid) { + VIR_DEBUG("In userns uid is %d, gid is %d\n", + uid, gid); + errno = EINVAL; + + virReportSystemError(errno, + _("[userns] Src dir '%s' does not belong to uid/gid: %d/%d"), + vmDef->fss[i]->src, uid, gid); + return -1; + } + } + + return 0; +} + /** * lxcContainerStart: * @def: pointer to virtual machine structure @@ -1866,6 +1909,9 @@ int lxcContainerStart(virDomainDefPtr def, if (userns_supported()) { VIR_DEBUG("Enable user namespace"); cflags |= CLONE_NEWUSER; + if (lxcContainerUsernsSrcOwnershipCheck(def) < 0) { + return -1; + } } else { virReportSystemError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("Kernel doesn't support user namespace"));
Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
On Fri, Aug 09, 2013 at 04:05:58PM +0800, Chen Hanxiao wrote:
From: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
If we enable userns, the ownership of dir we provided for containers should match the uid/gid in idmap. Currently, the debug log is very implicit or misleading sometimes. This patch will help clarify this for us when using debug log or virsh.
v2: syntax-check clean
Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com> --- src/lxc/lxc_container.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 46 insertions(+), 0 deletions(-)
diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c index b910b10..2ccdc61 100644 --- a/src/lxc/lxc_container.c +++ b/src/lxc/lxc_container.c @@ -1815,6 +1815,49 @@ lxcNeedNetworkNamespace(virDomainDefPtr def) return false; }
+/* + * Helper function for helping check + * whether we have enough privilege + * to operate the source dir when userns enabled + * @vmDef: pointer to vm definition structure + * Returns 0 on success or -1 in case of error + */ +static int +lxcContainerUsernsSrcOwnershipCheck(virDomainDefPtr vmDef) +{ + struct stat buf; + size_t i; + uid_t uid; + gid_t gid; + + VIR_DEBUG("vmDef->nfss %d", (int)vmDef->nfss); + for (i = 0; i < vmDef->nfss; i++) { + VIR_DEBUG("dst is %s, src is %s", + vmDef->fss[i]->dst, + vmDef->fss[i]->src); + + uid = vmDef->idmap.uidmap[0].target; + gid = vmDef->idmap.gidmap[0].target; + + if (lstat(vmDef->fss[i]->src, &buf) < 0) { + virReportSystemError(errno, _("Cannot access '%s'"), + vmDef->fss[i]->src); + return -1; + } else if (uid != buf.st_uid || gid != buf.st_gid) {
Comparing the uid/gid owner of a file is not an accurate check. For example, a file could have ACLs set which allow access even when the uid/gid do not match. I think we should focus on improving the error messages reported when we hit the actual problem rather than trying to pre-guess the problem and potentially get it wrong. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
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Chen HanXiao -
Chen Hanxiao
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Daniel P. Berrange